I. Field of the Invention
The present invention relates to anti-theft fasteners and securing devices, and more particularly to an anti-theft device adapted for use in securing a removable body part on a microscope stand to prevent theft of the removable body part.
II. Description of the Related Art
Microscopes used at universities, hospitals, and other research facilities are typically configured in modular fashion, whereby a removable body part is mounted on the microscope stand. A common removable body part is a viewing unit such as a binocular viewing unit, a bridge viewing unit for allowing more than one observer, or a camera viewing unit. In established modular microscope designs, the stand is provided with a guide for locating the removable body part on the stand, and a common thumbscrew is threaded by hand through the guide portion of the stand to engage a portion of the removable body part to fix the body part in a selected position. In the case of a viewing unit, an annular dovetail is typically provided at the base of the viewing unit and a corresponding annular dovetail guide is provided on the top of the microscope stand; a tapped hole for a thumbscrew extends radially through the dovetail guide of the stand. Accordingly, the viewing unit can be rotated about an optical axis of the microscope and then secured in a selected rotational position by a thumbscrew tightened radially inward to engage the dovetail of the viewing unit. As an alternative to using a common thumbscrew having no moving parts, it is also known to use a thumbscrew incorporating a spring-biased ball plunger.
Two main drawbacks are recognized with respect to the prior art mentioned above. First, it is possible for a user to loosen the thumbscrew and completely remove the viewing unit or other removable body part from the stand, a situation that has enabled widespread theft of these expensive and vital microscope parts. Second, the thumbscrews can be completely unscrewed and removed from the tapped hole in the microscope stand, resulting in inadvertent loss of such thumbscrews.
Therefore, it is an object of the present invention to provide a securing device that prevents theft of removable microscope body parts.
It is another object of the present invention to provide a securing device that prevents theft of removable microscope body parts while being operable in a simple manner without a tool between a partial release state that allows a user to adjust the position of the removable body part and a locking state that fixes the position of the removable body part.
It is yet another object of the present invention to provide a securing device that remains completely with the microscope body to prevent loss of the device.
It is yet another object of the present invention to meet the above objects with a simple and inexpensive device.
In furtherance of these and other objects, an anti-theft device formed in accordance with the present invention comprises a tubular housing threaded at its leading end for mating with a tapped hole in mounting guide means of a microscope stand, a plunger received by an axial passageway in the housing and movable in extension and retraction directions within a limited range, and a driver partially received within the passageway to extend from a trailing end of the housing. The driver includes an enlarged externally threaded portion sized for mating with an internally threaded portion of the housing, such that the driver can be threadably advanced to abut with the plunger to prevent motion of the plunger in its retraction direction. Alternatively, the driver can be unscrewed so as to allow the plunger to move in its retraction direction. A snap ring is provided near the trailing end of the housing to prevent complete withdrawal of the driver from within the housing passageway.
The housing is threaded into the tapped hole and tightened using a tool, such as a wrench, for which the housing is adapted. An enlarged head on the driver enables a user to threadably advance the driver by hand such that the driver pushes the plunger against a portion of the removable body part to securely fix the removable body part""s position, or to withdraw the driver in an opposite direction until threaded mating is disengaged and the driver spins freely, whereby the plunger can travel slightly in its retraction direction so as to enable the removable body part to be adjusted within the guide but not completely removed from the guide. To remove the device, the tool must be used to loosen the device housing from the tapped hole in the microscope stand.